public class Solution {
    public int removeDuplicates(int[] nums) {
        int n = nums.length;
        if(n <= 2){
            return 2;
        }
        int slow = 2, fast = 2;
        while(fast < n){
            if(nums[slow - 2] != nums[fast]){
                nums[slow] = nums[fast];
                slow++;
            }
            fast++;
        }
        return slow;
    }
}
